Author(s): VONDERSCHER, M., SAMOZINO, P., BOWEN, M., MOREL, B., Institution: UNIVERSITÉ SAVOIE MONT BLANC, Country: FRANCE, Abstract-ID: 2076

INTRODUCTION:
Critical intensity is an important fatigue threshold with considerable potential for enhancing performances or quality of life of individuals experiencing chronic diseases (1). Traditionally, critical velocity (Vc) is assessed from 3 to 5 tests-to-exhaustion, time-trials (TT) or all-out, making regular assessments of athletes or frail populations challenging. Recently, Bowen et al. (2) formalised a mathematical model that describes the evolution of maximal capacities at any time of severe exercises. This model, along with the Vc concept suggests that maximal velocity (Vmax) decreases when running above Vc and recover for intensity below Vc. Thus, performing a decreasing ramp starting above and finishing below Vc, Vmax is assumed to decrease and then rise again, the ramp value at switch point corresponding to Vc. Based on this idea, the Ramp Above Critical Level Endurance Test (RACLET) has been validated in cycling (3). The RACLET consists in a 5-min non-exhaustive test following a decreasing ramp velocity target during which ~3s sprints assess Vmax every 30s. This study aimed to test the reliability and validity of the RACLET during running.
METHODS:
17 participants completed 4 sessions separated by 24h, starting with a 30-min standardised warmup. Session 1 included 2 identical RACLET separated by a 10-min rest, and during which participants running velocity was measured using GPS (GPexe, 18Hz). RACLET started at 65% of the initial maximal velocity (Vi) and gradually decreased to reach 3m/s at 5min. To maintain the target pace, participants followed a pacing bike that shifted to the side during sprints. Sessions 2 to 4 included randomised TT on 400, 1500 and 3000m. Vmax reached during each sprint of the RACLET or mean velocity performed during the TT allowed to fit the following equation: Vmax(t)=Vi–(1/Tau)*(int(V(t)-Vc)dt) where V is the target velocity and Tau is a time constant. Vc reliability was quantified using SEM and ICC between the 2 RACLET. Validity was assessed using systematic and random errors compared with the gold standard method (TT).
RESULTS:
Mean Vc was 13.5±2.1km/h on RACLET. This value is in line with data reported in the literature (4). Vc determined with RACLET showed good absolute (SEM=3.7%) and relative (ICC=0.95) reliability and presented a good concurrent validity with low systematic (0.1km/h; 1.3%) and random (0.7km/h; 5.6%) errors. Vc obtained from RACLET and TT were highly correlated (r=0.95, p<0.001).
CONCLUSION:
The RACLET is a valid and reliable method to assess Vc in running. This test has the advantage of being short, carried out in a single session and mainly submaximal (excluding short Vmax evaluations). The RACLET is interesting for research purposes to evaluate Vc (e.g. for experimental designs with numerous conditions) but also for follow-up monitoring requiring frequent reassessment of Vc, which was hitherto difficult to do.
REFERENCES:
Poole et al., MSSE, 2016
Bowen et al., JTB, 2023
Bowen et al., ECSS, 2023
Kramer et al., EJAP, 2020